1. Field of Invention
The present invention relates generally to a vascular filters for capturing, depending on the embodiment described and its use, embolic particles or embolic agents. In one aspect, the present invention relates to an treatment system utilizing a protection device which reduces the reflux of a treatment agent in a blood vessel during an embolization therapy procedure, where the embolization agent is delivered through a catheter to provide therapy to tissue distal via a delivery orifice of the catheter. In another embodiment, the invention relates to a system used in combination with a thrombus retrieveal system for protecting the patent from released embolic particles during thrombus retrieval.
2. State of the Art
Embolization, chemo-embolization, and radio-embolization therapy are often clinically used to treat a range of diseases, such as hypervascular liver tumors, uterine fibroids, secondary cancer metastasis in the liver, pre-operative treatment of hypervascular menangiomas in the brain and bronchial artery embolization for hemoptysis. An embolizing agent may be embodied in different forms, such as beads, liquid, foam, or glue placed into an arterial vasculature. The beads may be uncoated or coated. Where the beads are coated, the coating may be a chemotherapy agent, a radiation agent or other therapeutic agent. When it is desirable to embolize a small blood vessel, small bead sizes (e.g., 10 μm-100 μm) are utilized. When a larger vessel is to be embolized a larger bead size (e.g., 100 μm-900 μm) is typically chosen.
While embolizing agent therapies which are considered minimally or limited invasive therapies have often provided good results, they have a small incidence of non-targeted embolization which can lead to adverse events and morbidity. One cause of non-targeted delivery of embolizing agents is reflux in the artery. Reflux occurs where the embolic agent exits the distal end of the catheter and then backflows around the outside of the catheter. This backflow can end up in a healthy organ and damage it.
Reflux can also occur during the administration of the embolization agent, while the artery is still patent. Reflux may also occur when the artery becomes static and injected embolizing agents flow backward.
Additionally, reflux can be a time-sensitive phenomenon. Sometimes, reflux occurs as a response to an injection of the embolic agent, where the reflux occurs rapidly (e.g., in the time-scale of milliseconds) in a manner which is too fast for a human operator to respond. Also, reflux can happen momentarily, followed by a temporary resumption of forward flow in the blood vessel, only to be followed by additional reflux.
FIG. 1 shows a conventional (prior art) embolization treatment in the hepatic artery 106. Catheter 101 delivers embolization agents (beads) 102 in a hepatic artery 106, with a goal of embolizing a target organ 103. It is important that the forward flow (direction arrow 107) of blood is maintained during an infusion of embolization agents 102 because the forward flow is used to carry embolization agents 102 deep into the vascular bed of target organ 103.
Embolization agents 102 are continuously injected until reflux of contrast agent is visualized in the distal area of the hepatic artery. Generally, since embolization agents 102 can rarely be visualized directly, a contrast agent may be added to embolization agents 102. The addition of the contrast agent allows for a visualization of the reflux of the contrast agent (shown by arrow 108), which is indicative of the reflux of embolization agents 102. The reflux may, undesirably, cause embolization agents 102 to be delivered into a collateral artery 105, which is proximal to the tip of catheter 101. The presence of embolization agents 102 in collateral artery 105 leads to non-target embolization in a non-target organ 104, which may be the other lobe of the liver, the stomach, small intestine, pancreas, gall bladder, or other organ.
Non-targeted delivery of the embolic agent may have significant unwanted effects on the human body. For example, in liver treatment, non-targeted delivery of the embolic agent may have undesirable impacts on other organs including the stomach and small intestine. In uterine fibroid treatment, the non-targeted delivery of the embolic agent may embolize one or both ovaries leading to loss of menstrual cycle, subtle ovarian damage that may reduce fertility, early onset of menopause and in some cases substantial damage to the ovaries. Other unintended adverse events include unilateral deep buttock pain, buttock necrosis, and uterine necrosis.
Often, interventional radiologists try to reduce the amount and impact of reflux by slowly releasing the embolizing agent and/or by delivering a reduced dosage. The added time, complexity, increased x-ray dose to the patient and physician (longer monitoring of the patient) and potential for reduced efficacy make the slow delivery of embolization agents suboptimal. Also, reducing the dosage often leads to the need for multiple follow-up treatments. Even when the physician tries to reduce the amount of reflux, the local flow conditions at the tip of the catheter change too fast to be controlled by the physician, and therefore rapid momentary reflux conditions can happen throughout infusion.
In a different and unrelated area of known art, thrombus retrieval procedures are carried out in the cardiac, pulmonary, neurovasculature systems. In many cases, specialized thrombus capture devices are employed to mechanically capture a thrombus and remove it from the arterial vasculature. Three products currently available in the market, the SOLITAIRE STENTRIEVER device from Covidien, the MERCI RETRIEVAL SYSTEM from Concentric Medical, Inc., and the PENUMBRA SYSTEM from Penumbra Inc., are all effective at recanalizing a vessel. All three devices require aspirating the thrombus into a larger inner diameter catheter placed proximal to the thrombus location. After the thrombus is captured, two important steps are required: first, the thrombus needs to be dragged backward toward the larger inner diameter catheter, and second the thrombus needs to be pulled into the catheter.
However, the initial capture, the transport, and the aspiration of the thrombus generates a shower of embolic particles which end up either distal to the intervention zone, proximal to the intervention zone, or in branching collaterals which are in the intervention zone. This shower of embolic particles may be responsible for the low percentage of positive patient outcomes (25%-45%) after 90 days even though there is a very high recanalization rate (50%-85%).